Standard zirconia toughened alumina (ZTA) is produced in industry by taking alpha alumina (α-Al2O3) and adding 10-25 percent by weight of tetragonal zirconia polycrystals (TZP) to strengthen and toughen the alumina as taught by Hori in U.S. Pat. No. 4,532,224. TZP is a tetragonal form of zirconia, this tetragonal crystal structure phase is a metastable form of the zirconia that is stabilized by a stabilizing agent so as not to revert back to the monoclinic crystal structure phase upon cooling from the sintering temperature. Common stabilizing agents are Y2O3 and CeO2 that when combined with zirconia (ZrO2) in an effective composition gives rise to TZP. Standard ZTA of 10-25 weight percent TZP has a theoretical density of 4.10-4.35 g/cc and strength of greater than 80 kpsi. Hori showed for compositions of TZP below 10-percent by weight that the strength of the alumina drops significantly to around 48 kpsi, near that of just pure alumina. However, pure alumina is much lighter with a theoretical density of around 3.98 g/cc.
Lighter weight formulations of ZTA with high strength have been difficult to produce. Lighter weight, stronger ZTA has applications in armor and wear-tiles for chimney chutes where lower density coupled with higher strength is required. It is the goal of the present patent application to provide a lighter weight and stronger formulation of ZTA.